Boxing: Manny Pacquiao to undergo shoulder surgery

Trainer Freddie Roach (left) speaks to his fighter Manny Pacquiao of the Philippines between rounds during his welterweight unification bout against US boxer Floyd Mayweather Jr., at the MGM Grand Garden Arena in Las Vegas, Nevada on May 2, 2015. Man
Trainer Freddie Roach (left) speaks to his fighter Manny Pacquiao of the Philippines between rounds during his welterweight unification bout against US boxer Floyd Mayweather Jr., at the MGM Grand Garden Arena in Las Vegas, Nevada on May 2, 2015. Manny Pacquiao will undergo surgery this week for a torn rotator cuff. -- PHOTO: AFP

(REUTERS) - Manny Pacquiao will undergo surgery this week for a torn rotator cuff, with the recovery time expected to put the Filipino out of action for 9-12 months, ESPN.com said on Monday.

Pacquiao claimed a shoulder injury hampered his bid to hand Floyd Mayweather a first loss as a professional in the richest fight in boxing history at the MGM Grand Garden Arena in Las Vegas on Saturday.

Mayweather won a unanimous decision in the four-belt unification bout to improve his record to 48-0.

The injury would appear to rule out any chance of a rematch after the 38-year-old Mayweather said he would have one more fight in September before retiring. "We have an MRI scan that confirms he has a rotator cuff tear. He has a significant tear," orthopedic surgeon Neal ElAttrache told ESPN.com.

Pacquiao (57-6-2, 38 KOs), known for his aggressive and all-out attacking style, was clearly not the his typical offensive-minded self in Las Vegas.

After the fight, Top Rank promoter Bob Arum said Pacquiao suffered a shoulder injury in training camp about two-and-a-half weeks earlier and that it hampered him in the fight.

Top Rank and Pacquiao confirmed the account of the injury in a statement on Monday, saying that the 36-year-old and his doctors had concluded that with rest, treatments and monitoring, he would be ready for the fight.

However, they said the Nevada Commission stopped the treatment a few hours before the fight, telling them it was unaware of the shoulder injury.